In the recent years, in dwelling houses or so forth employing various newly developed building materials, such as laminated plywood and the like, it has been pointed out that toxic gas of volatile organic compound, such as formic aldehyde and the like, discharged from the newly developed building materials, and such gas should have harmful influence on a living environment. On the other hand, ammonia gas generated from a concrete or paint may promote degradation of exhibits in art museums and museums, or may be a cause of generation of faulty products in a clean room, such as semiconductor manufacturing factories and so forth. Therefore, demand for collection of the toxic gas in the ambient air and analysis of gas concentration, is getting stronger. For providing a measure for such problem of toxic gas, it has been quite important to measure a concentration of toxic gas component in the ambient air, to investigation of a gas generation source and to know a discharge speed of the gas.
As a method for collecting an inspection objective gas, such as toxic gas or the like, a method to condensingly collect a fine amount of gas has been employed, in which a gas collecting system is constructed with a collecting vessel filled with a collecting liquid, an air pump, a drying agent, a flowmeter, a volume flowmeter (integrating flowmeter) and so forth. In an inspection site, an ambient air is introduced into the collecting liquid with measuring a suction amount to continuously cause bubbling by the ambient air in the collecting liquid to dissolve the inspection objective gas in the ambient air into the solution for condensing collection. Then, by analysis of the collecting liquid by a chemical method to dissolve a gas component in the solution is derived to convert into a concentration in the sucked ambient air.
On the other hand, by JIS (Japanese Industrial Standard) A 5908 "particle board", there has been defined a method for measuring a discharge amount of formic aldehyde discharged from a wooden building materials. The method is to introduce a material to be inspected with cutting into a narrow paper tablet like piece into a glass desciccator together with distilled water contained in a tray, to leave for a predetermined period to naturally dissolve formic aldehyde into the distilled water for collection.
However, in the former gas collecting system, it becomes necessary to appropriately control a gas flow rate (flow velocity) for making a gas collection rate constant to read variation of indicia of a gas volumeter with measuring a period by a stop watch, or to frequently adjust a flow velocity by a needle valve with connecting an instantaneous flowmeter. Therefore, in the conventional gas collecting system, it is significantly troublesome for adjustment of flow rate or reading of a gas suction amount. In conjunction therewith, the gas volumeter is precision mechanical equipment, and thus is required sufficient attention in handing for expensiveness and sufficient level of skill. Also, an equipment and material for collection becomes large scale to cause difficulty in transportation of the equipment and material and in movement among inspection sites to make it troublesome for installation and adjustment to make gas collecting operation cumbersome.
On the other hand, in the later method, by inspecting the distilled water, in which formic aldehyde is collected, a gas discharge amount per a unit period can be predicted. However, in this method, it is required to cut a testing piece from the material to be inspected. Therefore, it is not possible to perform inspection for the building completely constructed to limit range of application.